ABSTRACT
It has been shown that the blood sugar in the adult fowl, male or female, after falling during the first 2 days of fasting, rises on the 3rd or 4th day and then declines rapidly so that a well-defined peak is formed (Henry, Macdonald and Magee, 1933). This change was so constant in its occurrence that experiments were undertaken in the hope of throwing light on the immediate cause. As all the original glycogen stores are almost certainly exhausted after fasting for 3 or 4 days, the increase in blood sugar could only have come from protein or fat. A study was therefore made in fasting fowls of the uric acid and non-protein nitrogen contents of the blood, in the hope that, if any marked change in the metabolism of protein occurred, it would be reflected in alterations in the amounts of these present in the blood. In regard to fat the metabolites chosen were cholesterol and lecithin. The significance of these substances in fat metabolism is not very clear at present; but, as they can be readily and accurately estimated in small amounts of blood, they were preferred to blood fat as possible indicators of change in fat metabolism. The liver and muscle glycogen of fowls killed after different periods of fasting were also determined, as well as the effect of fasting on the respiratory exchange. Marked qualitative alterations in energy metabolism would, it was thought, be associated with corresponding changes in the R.Q. None of these lines of study threw any direct light on the problem we set out to solve ; but the results obtained were considered to be of sufficient interest in themselves to merit publication.
